An efficient multiple-mode molecular logic system for pH, solvent polarity, and Hg ions

A novel fluorophore 1,3-bis(1,1,3-trimethyl-1H-benzoe]indol-2(3H)-ylidene)propan-2-one (L) was synthesized and fully characterized by ¹H NMR, ¹³C NMR, HRMS, and X-ray single-crystal structural analysis. Compound L is a pH-controlled molecular switch due to its protonation. The fluorescence change in protic polar solvents means that this compound also could be used as a protic solvent polarity sensor. Among the considered metal ions, the fluorescence of compound L could be quenched completely by Hg²⁺ ions with a high selectivity. Based on these fluorescence characters, this fluorescent dye L has promising applications as a multiple-mode molecular logic system.